Avengers: Rebirth
Between "Rebirth" and "Reborn", something about birth...it being a verb rather than an adjective I suppose, makes it feel grander, more cosmic.
It would also have multiple meanings; not only the reassembly of the original Avengers and the prospective rebirth of those lost in "Infinity War," but also heralding a rebirth of the Marvel Cinematic Universe itself, reconstituting its landscape for both the departures of old characters and the establishment of new characters...passing the torch as it were.
And departure merely meaning retirement...though, of course, death is another, very likely, probably inevitable option.
Who knows what they go with, whether or not "Infinity" is kept as a through line, but a theme of resurrection feels appropriate...without using the word "Resurrection" of course; the Alien and Halloween franchises are ample proof that using that word in your title is meh haha